Field of the Invention
The present invention relates to a display device integrated with a touch screen.
Discussion of the Related Art
With the development of information society, various demands for display devices for displaying picture images have been increased. Recently, various display devices such as liquid crystal display (LCD), plasma display panel (PDP), and organic light emitting diode (OLED) display device have been used.
Such a display device provides a touch based input mode that enables a user to easily, intuitively and conveniently input information or command, instead of a conventional input mode such as button, keyboard, and mouse.
In order to provide such a touch based input mode, it is required to identify a touch or non-touch of a user and exactly detect a touch coordinate.
To this end, according to the related art, one of various touch modes such as a resistance film mode, a capacitance mode, an electromagnetic induction mode, an infrared mode, and an ultrasonic mode is adopted to provide touch sensing.
Among the various touch modes, the capacitance touch mode is widely adopted, which detects a touch or non-touch and a touch coordinate through a plurality of touch electrodes (for example, horizontal electrode and vertical electrode) formed in a touch screen panel on the basis of variation of capacitance between the touch electrodes or capacitance between the touch electrodes and a pointer such as a finger.
In case of the capacitance touch mode, in addition to capacitance required for touch sensing, parasitic capacitance is formed between a rear resistance film in the periphery of the touch electrodes and another voltage line (gate line and data line) and between the touch electrodes.
Load of touch driving is increased and accuracy of touch sensing is reduced due to such parasitic capacitance which is formed unnecessarily. In serious case, a problem may occur in that touch sensing becomes impossible. The problem caused by unnecessary parasitic capacitance may occur more seriously in a medium or large sized display.
Also, the problem caused by unnecessary parasitic capacitance often occurs in a display device integrated with a touch screen, in which a touch screen panel (TSP) is built in a display panel in an in-cell type, and acts as a factor that precludes realization of a medium or large sized in-cell type touch screen panel.
For example, as shown in FIG. 1, in case of a general display device integrated with an in-cell type touch screen, a panel is driven by time division in accordance with a display period and a touch period. In other words, if a driving mode of the panel is a display driving mode, a common voltage (voltage level: a) is applied to a plurality of electrodes, whereby the plurality of electrodes act as display electrodes. If the driving mode of the panel is a touch driving mode, a touch driving signal (touch signal) is applied to the plurality of electrodes, whereby the plurality of electrodes act as touch electrodes. In this touch driving mode, unnecessary parasitic capacitance occurs among a rear resistance film, a gate line, a data line, and a common electrode, whereby touch sensing accuracy may be reduced or touch sensing may become impossible.